Hydraulic actuated drill collar



Oct. 1, 1963 J. M. KELLNER 3,105,561

HYDRAULIC ACTUATED DRILL com 4 Sheets-Sheet 1 FIG. 1B

Jackson M. Kellner Inventor By 4. Attorney Oct. 1, 1963 KELLNER 3,105,561-

HYDRAULIC ACTUATED DRILL COLLAR Filed Sept. 13, 1960 4 Sheets-Sheet 2 Jackson M. Kellner Inventor 8W 4'. Aii'orney United States Patent 3,105,561 HYDRAULIC ACTUATED DRILL COLLAR Jackson 1%. Kellner, Tulsa, Gillan, assignor to Jersey Production Research Company, a corporation of Dela- Ware Filed Sept. 13, 1960, Ser. N 55,751 19 Claims. {$1. 175-234)) This invention relates to apparatus for applying weight to a bit as used in the drilling of wells or boreholes into the earth. More particularly, it relates to a bottom hole assembly wherein hydraulic drilling fluid pressure is used to exert force on a bit during the drilling of wells.

In the art of drilling wells for the production of oil and gas, for example, the most commonly used method is the rotary drilling method. Conventional practice in rotary drilling involves the use of a drill bit attached to the lower end of a string of drill pipe which is supported and rotated at the surface of the earth. In conventional practice, a drilling fluid is continuously circulated through the rotating drill pipe to the bottom of the well, through the drill bit, and thence back to the surface by way of the annular space between the well wall and drill pipe. The drilling fluid usually comprises a liquid such as water, or a clay base mud, or an oil base mud, or an emulsion mud. More recently, pneumatic fluids such as gas or air are being used as drilling fluids. The purpose of the drilling fluid includes cool ing the bit, carryin cuttings out of the well and also to impose a hydrostatic pressure upon high pressure formations penetrated by the drill bit to prevent the uncontrolled escape of oil, gas or water during drilling operations.

Rotary drilling practice has found that the rate of penetration of a drilling bi-t through subterranean formations is increased by increasing the force of the drill bit against the bottom of the well. It has been further found that the drilling of a straighter hole is accomplished by creating a localized force in the area immediately adjacent the drill bit. In the latter instance, the twisting and rotative movement of lengthy strings of relatively flexible drill pipe is straightened immediately adjacent the drill bit by the application of such force.

Heretofore increased drilling rate and a straighter hole have been accomplished by the addition of one or more heavy drill collars between the drill bit and drill string, usually immediately above the drill bit. Modern drilling practices have indicated a trend toward even higher bit weights resulting in maximum drilling rates and accordingly minimum footage costs. The use of the heavy drill collars, however, has not been completely satisfactory. Their advantages have been offset by the needfor heavier surface lifting equipment, longer rig-time in pulling the drill pipe, drill collars, and drill bit when the latter is required to be changed.

Accordingly it is a primary object of this invention to provide apparatus which overcomes the objections of the prior art methods for increasing drilling rate and efflciency.

An additional object of this invention is to provide an apparatus for use in the drilling of Wells wherein a drilling fluid is utilized to apply force upon the drill bit thereby eliminating the handling of long strings of drill collars.

Another object of this invention is to provide an apparatus for applying hydraulic pressure force to a rotary drilling bit and which is operative automatically as drilling progresses.

A still further object of this invention is to provide apparatus for applying hydraulic pressure to a rotary .2 drilling bit which is readily adapted to be positioned along a len th of drill pipe to become a part of the drilling system.

A yet still further object of this invention is to provide apparatus for applying hydraulic drilling fluid pressure to intermittently and automatically anchor all outer housing to a well or borehole wall with respect to a rotating drill pipe and substantially simultaneously apply igh pressure to a drilling bit.

These and other objects of this invention will become more apparent upon further reading of the specification and claims when taken in conjunction with the following illustrations of which:

FIGURES 1A and 1B are elevational "lC-WS partially in section which when taken together illustrate the preferred embodiment and apparatus of this invention.

FIGURE 2 is a sectional view taken along the line 22 of FIGURE 1A.

FIGURE 3 is a sectional view taken along the line 3-3 of FIGURE 1A. a

FIGURE 4 is a sectional view taken along the line 44 of FIGURE 18.

FIGURE 5 is a sectional view taken along the line 5-5 of FIGURE 13.

"FIGURES 6, 7, 8 and 9 are enlarged fragmentary sectional views of the valve mechanism representing various operational positions of the valve according to the preferred embodiment of this invention.

Briefly, in a preferred embod'unent this invention concerns an automatic resetting hydraulic dnill collar adapted for use in the rotary drilling of wells and which generally includes an inner mandrel and outer mandrel, case, or housing. The differential pressure existing across a drill bit attached to the inner mandrel as drilling fluid passes therethorugh, is utilized first to anchor the outer mandrel to the well wall with respect to the rotating and drilling inner mandrel and second, apply force to the drill bit. A snap acting valve arrangement operable by movement of the inner mandrel controls the releasing of the anchored outer mandrel and the resetting of same to repeat the process.

Description Referring now to the drawings in greater detail and in particular. FIGURES 1A and 1-13, the numeral 29 refers to an inner mandrel which is attached at its lower .end to a drill bit, such as a jet type bit, in which there are restricted passageways 24 to cause a pressure differential across the bit nozzles and across the inner passageway 23 and the annular space 25 of the well. Other choke or other fluid flow regulating systems can be used to obtain the desired pressure differential. A connecting collar 22 at the upper end of the inner mandrel is adapted for attachment to a rotary drill stem, not shown. Longitudinally and rotatably movable about the inner man rel is outer mandrel or housing or casing 26 which is sealed and supported at its upper end by Wiper 28, fluted rubber bearing 30 and main seal or packing 32. Similarly the lower end of the outer mandrel 26 is sealingly and rotatively supported by fluted rubber bearing 34 and seal or packing 36. The upper interior portion of the outer mandrel definesa first pressure cylinder or chamber 38 which preferably terminates at its upper end with a throttling cylinder 3?. A first pushdown piston 49 attached to the inner mandrel is adapted for reciprocating movement in cylinder space 38. A seal ring 42, of the cup type, for example, forms an upper pressure actuating cylinder. Pressure delay piston 43 is formed as a part of pushdo'wn piston 46 and is adapted for throttling movement with respect to cylinder space 39. An exhaust port 44 is located in the lower part of pressure cylinder 38 in order that the bottom side of piston 40 3 is exposed tothe relatively lower pressure existing in the annular space 25 during operation as hereinafter described.

Immediately below first cylinder 38 is a second pressure cylinder 46 formed interiorly of the outer mandrel 26 and sealed above and below by fluted rubber bearings 54 and 60 and mandrel seal or packing 56 and 58 respectively. Located in the upper end of cylinder 46 is throttling cylinder 47 which cooperates with the pressure delay piston 48 formed in the upper part of second power or pushdown piston 49 which is attached and formed as a part of inner mandrel 20. In the preferred embodiment of the invention, the second power piston 49 is formed with upper and lower opposed seal rings 50 and 52 respectively, to form upper and lower pressure actuating cylinders with respect to inner space 46.

Anchor shoe pressure chamber 68 is formed and sealed in the lower portion of outer mandrel 26 about inner mandrel by the lowermost packing and bearing 34 and 36 and seal 64 and bearing 66. Difierential area formed by increasing the diameter of mandrel 20 in chamber 68 also acts as a pushdown piston. This area is defined by shoulder 126 on mandrel 20. Anchor shoes 70 are arranged about the periphery of the outer mandrel 26 and are actuated in response to pressure created within chamber 68. The individual anchor members 70 are typically composed of an expansi-ble material 72 such as rubber, sandwiched between and bonded to a movable central metal core 74 and fixed outer sleeve 76.

Preferably intermediate of the upper chambers 38 and 46 and lower chamber 68 above described is valve operating chamber 62 which is vented at 63 to the relatively nected to valve release cage 80 by a resilient spring means 90, typically a resilient elastomer material bonded to the valve 84 and release cage 80. Attached to the slide valve proper are a multiplicity of spring loaded latch fingers 92 and 94 which are adapted to be latched and unlatched by respective upper shoulder 114 and lower shoulder 116 attached to or made integral with inner mandrel 20. Positive stops 122 and 124 on inner mandrel 20 limit the vertical travel of valve 84 with respect to mandrel 20.

Valve 84'is operable to alternately connect pressure fluid supply. port 96 which is midway between shoulder 114 and shoulder 116 and extends across inner mandrel 20 from supply passage '23: (a) to ports 98 which interconnect with first passageway 100, or (b) to port 108 which interconnects with second passageway 110. First passageway 100 terminates its lower end with port 102 into anchor shoe pressure chamber 68 and extends upwand (see FIGURES 2, 3, 4, and through port 104 into the upper portion of second pressure cylinder 46, and port 106 above piston 40 intothe first pressure cylinder 38. Second passageway 110 extends from port 108 upward to a port 112 located in the lower part of second pressure cylinder 46. Ports 98 are suflicient in numbet or size to properly relieve the fluid vented from chambers 38 and 46, so this vented fluid does not interfere with venting offiuid from chamber 68, thereby allowing -full retraction of anchor shoe core 74. Although the invention has been described with particular regard to upper first and second position and cylinder means, it is to be understood that a pushdown section of one or a plurality of piston means may be used. It is to be understood further that hydraulic pressure in second passageway 110 is operable through port 112 into the lower part of pressure chamber 46 below 4 piston 49 to return or move the inner mandrel to the upper starting position with respect to the outer mandrel where the cycle of operation, as hereinafter described, is repeated. Accordingly, second passageway 110 may exist to one or a plurality of power return cylinders.

Operation In describing the operation of the preferred embodiment of this invention, attention is directed to the views of FIGURES 6, 7, 8, and 9 which illustrate in greater detail the valve-operating mechanism when taken in combination with the views of FIGURES 1A and 1B.

A rotary drill pipe, not shown, is attached through coupling 22 to inner mandrel 20 and bit 21. Drilling fluid is pumped downward through the interior of the rotating drill pipe and inner mandrel portion 23 to the bit, where it passes through jet orifice 24, creating a condition of diflerential pressure across the biti.e., a relatively high pressure within the inner mandrel passage 23 and a relatively low pressure in annular space 25. In the initial operation, the inner mandrel and valve mechanism is in that position shown in FIGURE 6. A small portion of the drilling fluid passes through supply ports 96 into the confined portion of D-type slide valve 84 and thence through port 98 into first annular passageway 100. Substantially instantaneously, this pressure is transferred into pressure chamber 68, forcing anchor shoes 7 0, and in particular the movable inner cores 74into anchor contact with the borehole wall. Since throttling pistons'43 and 48 are positioned initially within their corresponding throttling cylinders 39 and 47 respectively, thrust pressure is delayed until the anchor shoes have been positioned. Thereafter, the full pressure-area force relationship is applied to the upper part of power pistons 40 and 49 respectively, tending to force them downward with respect to outer mandrel 26. If desired, throttling can be accomplished by proper design of pressure line 100 to momentarily delay the application of full pressure to pushdown pistons 40 and 49. Then, throttling pistons 43 and 49 and throttling cylinders 39 and 47 can be eliminated.

Rotary drilling imparted through inner mandrel 20 to bit 21 continues, with slide valve 84 traveling therewith as drilling progresses, until such time as the lower part or face 118 of .valve release tube engages the lowermost portion or upward face 120 of intermediate chamber 62. Rotary drilling continues under the applied pressure force until the lower valve latch fingers 94 are released from latch shoulder 116 by engagement with lower release finger 83 formed as a part of release tube 80. The continued downward movement of slide valve 84 with respect to release cage '80 creates tension in spring means (see FIGURE 7). Upon its release, slide valve '84 is snapped upward, causing engagement of upper latch finger 92.. with latch holder 114 as shown in FIGURE 8. In that position, high pressure supply fluid is now diverted through port 96 into second passageway 1 10 through port 108. First passageway is now vented to the relatively low pressure annular space through port 98, valve release ports 82, and exhaust ports 63. Accordingly, this permits release of anchor shoes 70 by the action of the resilient expansible material 72 returning to a retracted position. Since a relatively high pressure exists in second passageway acting through port 112 and the lower part of pressure cylinder 46, the outer mandrel 26 is moved downward quickly with respect to inner mandrel 20.

As shown in FIGURE 9, contact of valve release cage 80 with the upper portion of intermediate chamber 62 forces release finger 81 into engagement with valve latch fingers 92, moving them from contact with latch holder 114. Similarly, due to the potential tension created in spring 90, valve 84 is snap-actingly forced downward. Latch fingers 94'are engaged with latch holders 116 to assume the starting position as shown in FIGURE 6 wherein the cycle as above stated is repeated.

An apparatus similar to the above description has been built and tested. It has a stroke of about two feet and in its tests has had a resetting time of seven seconds or less. It is, of course, understood that the length of the stroke may be varied.

Although the placement of the anchor shoes 7 ii is shown at the lowermost part of outer mandrel 26, this is not to be held as limiting. This is preferred, however, since anchored contact is made with the newest portion of the drilled well and greater restoring forces are provided to the bit from the drill string tension.

Although this invention has been described with reference to specific and preferred embodiments, it will be apparent that many modifications can be made without departing from the spirit and scope of this invention. Accordingly, this invention should be considered not to be limited to the embodiments herein described, but should be limited only by the scope of the appended claims.

The invention claimed is:

1. Apparatus for applying force to a drill bit in a well comprising: an inner mandrel attachable to said bit and adapted to supply pressure fluid to said bit, piston means attached to said inner mandrel, an outer mandrel sealingly movable about said inner mandrel to form a pressure cylinder with said piston means, pressure fluid responsive means in fluid communication with said cylinder and of a character to anchor said outer mandrel to said well, and means responsive to selected relative positions between said outer mandrel and said inner mandrel for intermittently entering and exhausting said pressure fluid into said cyclinder above said piston means.

2. Apparatus for applying hydraulic force to a rotary drilling bit in a well comprising: an inner mandrel attached to said bit and adapted to supply hydraulic pressure fluid through said bit, piston means attached to said inner mandrel, a first passageway in said inner mandrel to supply said hydraulic pressure fluid above said piston means, a second passageway in said inner mandrel to supply said hydraulic pressure fluid below said piston means; an outer mandrel sealingly movable about said inner mandrel to form a pressure cylinder with said piston means, pressure responsive means supported by said outer mandrel and in fluid communication with said first passageway to releasably anchor said outer mandrel to said well wall, and valve means responsive to selected relative positions between said inner mandrel and said outer mandrel operable to supply said hydraulic pressure fluid alternately to said first and second passageways.

3. Apparatus for applying hydraulic force to a rotary drilling bit in a well comprising: an inner mandrel attachable at its lower end to said bit and adapted to supply hydraulic high pressure fluid through said bit, aplurality of piston means attached to said inner mandrel, a first passageway in said inner mandrel to connect said high pressure fluid with the top side of said piston means, a second passageway in said inner mandrel to connect said high pressure fluid with the bottom side of said piston means; an outer mandrel sealingly movable about said inner mandrel and adapted to form pressure cylinders with said piston means; pressure responsive means attached to said outer mandrel and in fluid communication with said first passageway to releasably anchor said outer mandrel to said well, and valve means operable to supply said high pressure fluid alternately to said first and second passageways.

4. Apparatus for applying hydraulic force to a drilling bit in a well comprising: an inner mandrel attached at its lower end to said bit and adapted to supply hydraulic pressure fluid through said bit, a plurality of piston means attached to said inner mandrel, a first passageway in said inner mandrel to connect said hydraulic pressure fluid with the top side of said piston means, a second passageway in said inner mandrel to connect said hydraulic pressure fluid with the bottom side of at least one of said piston means; an outer mandrel sealingly movable about said inner mandrel and adapted to form an upper pressure cylinder with each said piston means, and a lower pressure cylinder with at least one of said piston means; pressure responsive means supported by said outer mandrel and in fluid communication with said first passageway to releasably anchor said outer mandrel to said well, and valve means operable to supply said hydraulic pressure fluid alternately to said first and second passageways.

5. Apparatus for applying force to a rotary drilling bit in a well comprising: an inner mandrel attached at its lower end to said bit and adapted to supply hydraulic pressure fluid through said bit; an outer mandrel longitudinally movable and sealed with respect to said inner mandrel to form interiorly an upper first cylinder space having a vent at the lower end, a second cylinder space, an intermediate vented valve operating chamber having an upper shoulder means and a lower shoulder means, and a second pressure chamber; pressure actuated anchor shoes in the lower end portion of said outer mandrel and operable by fluid within said second pressure chamber; first and second sealed piston means attached to said inner mandrel and movable in said first and second cylinder spaces from an upper position to a lower position during said drilling; a first passageway in said inner mandrel to connect the interior of said inner mandrel with the top side of said first and second piston means and said second pressure chamber; a second passageway in said inner mandrel to connect the interior of said inner mandrel with the bottom side of said second piston; and valve means actuated by contact with said upper shoulder means and said lower shoulder means of said intermediate chamber in the said upper and lower positions to connect said first and second passageways alternately With the interior of said inner mandrel and the exterior of said outer mandrel.

6. Apparatus according to claim 5 wherein said inner mandrel opposite said intermediate chamber includes upper and lower latch shoulders attached to said inner mandrel, a high pressure supply port and first and second passageway ports between said upper and lower latch shoulders and said Valve means includes a slide valve having upper and lower latch fingers adapted to engage said latch shoulders alternately, a release tube mounted about said inner mandrel, means resiliently connecting said release tube to said slide valve, and means to limit the longitudinal movement of said release tube.

7. Apparatus according to claim 5 wherein said upper first and second upper cylinders and pistons include means to throttle movement of said piston with respect to said outer mandrel initially.

8. A rotary drilling apparatus for drilling a borehole which includes a drill string and a bit, the improvement which comprises: a mandrel insertable within said drill string, said mandrel having a longitudinal passage therethrough for conveying fluid; an outer case mounted around said mandrel in a longitudinally slidable and rotatable relationship therewith; pushdown means positioned between said mandrel and said case for exerting a force on said mandrel longitudinally thereof in'the direction of said bit and for exerting the reaction thrust of such force on said case; hydraulically operable anchoring means attached to said outer case; conduit means establishing fluid communication between the interior of said mandrel and said hydraulically actuated anchor means; valve means operable to close said conduit means upon relative movement of said mandrel in one direction with respect to said outer case and to open said conduit means upon movement in the opposite direction of said mandrel with respect to said outer case; and means for moving said outer case downwardly with respect to said mandrel when said condnit means is closed by said valve means.

9. An apparatus for forcing a bit against the bottom or" a borehole comprising in combination: a mandrel attachable at its lower end to a drill hit, an outer case mounted around said mandrel in a longitudinally slidable and rotatable relationship therewith; pushdown means positioned between said mandrel and said case for exerting a force on said mandrel longitudinally thereof in the direction of said bit and for exerting the reaction thrust of such force on said case; anchor means attached to said outer case and operable upon actuation to transfer said reaction thrust to the borehole wall, means operable in a first condition to de-actuate said anchor means and said pushdown means and in a second condition to actuate said pushdown means and said anchor means, and means for delaying the actuation of said pushdown means until said anchor means have been actuated.

10. An apparatus for forcing a bit against the bottom of a borehole comprising in combination: a mandrel attachable at its lower end to said hit, an outer case mounted around said mandrel in a longitudinally slidable and rotatable relationship therewith, pu-shdown means positioned between said mandrel and said case operable to exert a force upon said mandrel longitudinally thereof in'the direction of said bit and for exerting the reaction thrust of such force on said case, anchor means attached to said outer case and of a character to transfer such reaction thrust to the borehole wall, means for exerting a force on said anchor means in the direction of the borehole wall when said mandrel reaches its uppermost position with respect to said outer case, means for actuating said pushdown means after the actuation of said anchor means, means to de-actuate said pushdown means and said anchor means upon said mandrel reaching its lowermost position with respect to said outer case, and means for exerting a downward force on said outer case upon de-actuating said pushdown means and said anchor means.

11. In a rotary apparatus for drilling a borehole including a drill bit and drill string assembly and means for circulating fluid through said assembly and said borehole, the improvement which comprises a mandrel connected within said drill string and including a conduit for the flow of said fluids t-herethrough, a case surrounding said mendrel and rotatably and longitudinally movable therewith between upper and lower positions, thrust transfer means interposed between said mandrel and said case and actuable to thrust said mandrel downward relative to said case, wall anchor means on said case actuable to lock said case to the wall of said borehole, control means operable upon said case reaching said lower position to sequentially actuate said wall anchor means and said pushdown means, said control means being further operable upon said case reaching its said upper position to de-actuate said wall anchor means and said pushdown means, and means operable upon said case reaching said upper position to return said case to said lower position.

12. In a rotary apparatus for drilling a borehole including a drill bit and drill string assembly together with means for supplying fluid under pressure through said drill string to said drill bit, the improvement which con prises a mandrel connected with said drill string and provided with a conduit to transmit said fluid therethrough, a housing surrounding said mandrel in a rotatable relation therewith and longitudinally movable between'preselected upper and lower positions relative thereto, reversiblethrust transfer means interposed between said mandrel andsaid housing and hydraulically actuatab-le to transfer thrust therebetween, hydraulically actuatable wall anchor means mounted on said housing and adapted upon actuation to anchor said case to the wall of said borehole, hydraulic power transfer means actuatable to transmit hydraulic power from fluid flowing through said mandrel conduit to said thrust transfer'means and said wall anchor means, control means cooperable with said power transfer means upon said housing reaching said lower position to sequentially actuate said wall anchor means and said thrust transfer means so as to anchor said housing to said wall and thereafter thrust said mandrel downward relative to said housing, said control means being further cooperable with said power transfer means upon said housing reaching said upper position to deactu-ate said wall anchor means and to reverse said thrust transfer means.

'13. Apparatus for applying force to a drill bit in a well comprising: an inner mandrel attachable to said bit and adapted to supply pressure fluid to said bit, piston means attached to said inner mandrel, an outer mandrel sealingly movable about said inner mandrel to form a I pressure cylinder with said piston means, pressure fluid responsive means suported by said outer mandrel and in fluid communication with said cylinder to anchor said outer mandrel to said well, means for impeding the actuation of said piston means until the pressure fluid responsive means have anchored said outer mandrel to said well, and means responsive to selected relative positions between said outer mandrel and said inner mandrel for intermittently entering and exhausting said pressure fluid into said cylinder.

14. Apparatus for applying hydraulic :force to a rotary drilling bit in a well comprising: an inner mandrel attached to said bit and adapted to supply hydraulic pressure fluid through said bit, piston means attached to said inner mandrel, a first passageway in said inner mandrel to supply said hydraulic pressure fluid above said piston means, a second passageway in said inner mandrel to supply said hydraulic pressure fluid below said piston means; an outer mandrel sealingly movable about said inner mandrel to for-m a pressure cylinder with said piston means, pressure responsive means supported by said outer mandrel and in fluid communication with said first passageway to releasably anchor said outer mandrel to said well wall, said first passageway being constructed to provide a throttling action vto momentarily impede the exertion of force upon said piston means, and valve means responsive to selected relative positions between said inner mandrel and said outer mandrel operable to supply said hydraulic pressure fluid alternately to said first and second passageways.

15. Apparatus for applying hydraulic force to a rotary drilling bit in a well comprising: an inner mandrel attachable at its lower end to said bit and adapted to supply hydraulic high pressure fluid through said bit, a plurality of piston means attached to said inne mandrel, a first passageway in said inner mandrel to connect said high pressure fluid with the top side of said piston means, a second passageway in said inner mandrel to connect said high pressure fluid with the bottom side of said piston means; an outer mandrel sealingly movable about said inner mandrel and adapted to form pressure cylinders with said piston means; pressure responsive means supported by said outer mandrel and in fluid communication with said first passageway to releasably anchor said outer mandrel to said well, said first passageway being constructed to forma throttling action eflect on the pressure of fluids therein such that said pressure responsive means are actuated prior to substantial relative movement between said piston means and said outer mandrel, and vmve means operable to supply said 'high pressure fluid alternately to said first and second passageways.

16. Apparatus for applying hydraulic force to a drilling bit in a well comprising: an inner mandrel attached at its lower end :to said bit and adapted to supply bydraulic pressure fluid through said bit, a plurality of piston means attached to said inner mandrel, a first passageway in said inner mandrel to connect said hydraulic pressure fluid with the top side of said piston means, a second passageway in said inner mandrel to connect said hydraulic pressure fluid with the bottom side of at least one of said piston means; an outer mandrel sealingly movable about said inner mandrel and adapted to form an upper pressure cylinder with each said piston means, and a lower pressure cylinder with at least one of said piston means; pressure responsive means attached to said outer mandrel and in fluid communication =with'said first passageway to releasably anchor said outer mandrel to said well, means for impeding relative movement between said piston means and said outer mandrel until the pressure responsive means have been actuated, and valve means operable to supply said hydraulic pressure fluid alternately to said first and second passageways.

17. Apparatus for applying force to a rotary drilling bit in a well comprising: an inner mandrel attached at its lower end to said bit and adapted to supply hydraulic pressure fluid through said bit; an outer mandrel longitudinally movable and sealed with respect to said inner mandrel to form interiorly an upper first cylinder space having a vent at the lower end, a second cylinder space, an intermediate vented valve operating chamber having an upper shoulder means and a lower shoulder means, and a second pressure chamber; pressure actuated anchor shoes in the lower end portion of said outer mandrel and operable by fluid within said second pressure chamber; first and second sealed piston means attached to said inner mandrel and movable in said first and second cylinder spaces from an upper position to a lower position during said drilling; a first passageway in said inner mandrel to connect the interior of said inner mandrel with the top side of said first and second piston means and said second pressure chamber; a second passageway in said inner mandrel to connect the interior of said inner mandrel with the bottom side of said second piston means; means to throttle initial movement of said piston means with respect to said outer mandrel; and valve means actuated by contact with said upper shoulder means and said lower shoulder means of said intermediat chamber in upper and lower positions to connect said first and second passageways alternately with the interior of said inner mandrel and the exterior of said outer mandrel.

18. Apparatus according to claim 17 wherein said inner mandrel opposite said intermediate chamber includes upper and lower latch shoulders attached to said inner mandrel, a high pressure supply port and first and second passageway ports between said upper and lower latch shoulders and said valve means includes a slide valve having upper and lower latch fingers adapted to engage said latch shoulders alternately, a release tube mounted about said inner mandrel, means resiliently connecting 10 said release tube to said slide valve, and moms to limit the longitudinal movement of said release tube.

19. A rotary drilling apparatus for drilling a borehole which includes a drill string and a bit, the improvement which comprises: a mandrel insertable within said drill string, said mandrel having a longitudinal passage therethrough for conveying fluid; an outer case mounted around said mandrel in a longitudinally slidable and rotatable relationship therewith; pushdown means positioned between said mandrel and said case for exerting a force on said mandrel longitudinally thereof in the direction of said bit and for exerting the reaction thrust of such force on said case; hydraulically operable anchoring means attached to said outer case; conduit means establishing fiuid communication between the interior of said mandrel and said hydraulically actuated anchor means; means to prevent substantial longitudinal movement between said mandrel and said case prior to the actuation of said anchor means; valve means operable to close said conduit means upon relative movement of said mandrel in one direction with respect to said outer case and to open said conduit means upon movement in the opposite direotion of said mandrel with respect to said outer case; and means for moving said outer case downwardly with respect to said mandrel when said conduit means is closed by said valve means.

References Qited in the file of this patent UNITED STATES PATENTS 556,718 Semmer Mar. 17, 1896 1,983,287 Grinnell et a1. Dec. 4, 1934 2,223,645 Solomen Dec. 3, 1940 2,474,453 Armitage June 28, 1949 2,537,413 Lawrence Jan. 9, 1951 2,684,835 Moore July 27, 1954 2,712,920 Cullen et a1. July 12, 1955 2,743,781 Lane May 1, 1956 2,877,822 Buck Mar. 17, 1959 2,901,044 Arnold Aug. 25, 1959 2,937,007 Whittle May 17, 1960 2,946,578 De Smaele July 26, 1960 

1. APPARATUS FOR APPLYING FORCE TO A DRILL BIT IN A WELL COMPRISING: AN INNER MANDREL ATTACHABLE TO SAID BIT AND ADAPTED TO SUPPLY PRESSURE FLUID TO SAID BIT, PISTON MEANS ATTACHED TO SAID INNER MANDREL, AN OUTER MANDREL SEALINGLY MOVABLE ABOUT SAID INNER MANDREL TO FORM A PRESSURE CYLINDER WITH SAID PISTON MEANS, PRESSURE FLUID RESPONSIVE MEANS IN FLUID COMMUNICATION WITH SAID CYLINDER AND OF A CHARACTER TO ANCHOR SAID OUTER MANDREL TO SAID WELL, AND MEANS RESPONSIVE TO SELECTED RELATIVE POSITIONS BETWEEN SAID OUTER MANDREL AND SAID INNER MANDREL FOR IN- 